Method of making annular grid structure

ABSTRACT

A method of manufacturing an annular grid structure (such as the cylindrical honeycomb drums employed by the pulp and paper making industry) from separate planar and waved strips, comprising the steps of helically winding the strips in alternate arrangement on the annular outer surface of a mandrel whereby the wound strips form an axial build-up of the grid structure on the mandrel, during said winding interconnecting adjacent coils of the strips by successively connecting portions of the planar strip with the waved strip as said portions of the planar strip are initially laid onto the mandrel while said portions being connected are substantially locally heated; and permitting the heated, connected portions of the planar strip to successively cool while wound on the mandrel, so as to stress the metal of the planar strips beyond the elastic limit.

[ 1 July 17, 1973 METHOD OF MAKING ANNULAR GRID STRUCTURE [75] Inventor: Lawrence A. Carlsmith, Amherst,

[73] Assignee: Improved Machinery, Inc., Nashua,

[22] Filed: Nov. 5, 1971 [21] Appl. No.: 196,074

3,568,302 3/197] Oehler et alm 29/4773 Primary Examiner-Richard Lazarus Attorney-Frank S. Troidl, David W. Tibbott and Robert R. Paquin 57] ABSTRACT A method of manufacturing an annular grid structure (such as the cylindrical honeycomb drums employed by the pulp and paper making industry) from separate planar and waved strips, comprising the steps of helically winding the strips in alternate arrangement on the annular outer surface of a mandrel whereby the wound strips form an axial build-up of the grid structure on the mandrel, during said winding interconnecting adjacent coils of the strips by successively connecting portions of the planar strip with the waved strip as said portions of the planar strip are initially laid onto the mandrel while said portions being connected are substantially locally heated; and permitting the heated, connected portions of the planar strip to successively cool while wound on the mandrel, so as to stress the metal of the planar strips beyond the elastic limit.

19 Claims, 5 Drawing Figures PATENHii JUL 1 mm FIG] INVENTOR LAWRENCE A. CARLSM/ TH ATTORNEY METHOD OF MAKING ANNULAR GRID STRUCTURE The present invention relates to the manufacture of annular honeycomb or grid structures such as, for example, the honeycomb drums employed by the pulp and paper making industry.

conventionally, as described in US. Pat. No. 3,320,399 assigned to the assignee of the present invention, annular grid structures of this type have been manufactured by methods wherein strip material is helically wound and welded to form axial build-ups of the structures while the latter are at least generally unsupported against distortion. During the manufacture of the structures by such prior methods, however, difficulties have been encountered in preventing shrinkage of the welds from causing tilting of the strips and radial distortion of the grid structures.

The principal object of the present invention is to provide a new and improved method for making an annular honeycomb or grid structure, such as, for example, the honeycomb drums employed by the pulp and paper making industry, which method is particularly adapted to prevent distortion of the structure during its manufacture.

Another object of the invention is to provide a new and improved method of the type set forth which is particularly adapted to permit relatively economical, highspeed manufacture of such a grid structure.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein the preferred form of the inventionhas been given by way of illustration only.

In accordance with the invention, an annular grid structure may be made from planar and connecting strip means by a method comprising the steps of progressively forming an axial build-up of the grid structure by winding the planar strip means in helical coils on a mandrel with the connecting strip means adjacent to the wound coils of the planar stripmeans, interconnecting the wound coils of the planar strip means and the connecting strip means while the wound coils of the planar strip means are substantially heated at the locations of the interconnections-to a temperature sufficiently great that cooling of the planar strip means from such temperature would, in the absence of the mandrel, cause substantial shrinkage of the planar strip means, and permitting the substantially locally heated wound coils of the planar strip means to cool while on the mandrel to a temperature sufficiently low that the mandrel prevents permanent shrinkage of the planar strip means from occuring due to such cooling and the planar strip means resultantly stretches.

Referring to the drawings:

FIGS. 1 through 4 schematically illustrate the practide of one embodiment of the method of the invention; and

FIG. 5 is a fragmentary, perspective view of a grid structure provided by the practice of such method.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts through out the several views, the method of the invention may be employed to manufacture an annular, cylindrical honeycomb or grid structure from a planar strip 12 and a separate waved or connecting strip 14, both of which strips l2, 14 are of stainless steel or other ductile metal. As shown in FIG. 5, the waved or connecting strip 14 may throughout its length include alternating diagonal segments 16 and connecting segments 18, adjacent ones of the connecting segments 18 being on opposite sides of the central longitudinal plane 20 of the waved strip 14 and the diagonal segments 16 crossing such central plane 20. Alternatively, however, the waved strip 14 may be of other suitable waved configuration capable of providing openings 22 through the grid structure 10 when the strips 12, 14 are interconnected in upstanding, juxtaposed relationship to form the latter.

In the practice of the illustrated embodiment of the invention, there is employed a cylindrical mandrel 24, preferably constructed of cast iron or steel, having a circumferential annular outer surface 26 of diameter the same as that of the inner circumference of the cylindrical grid structure 10 to be manufactured; and the mandrel 24 is initially positioned on a turntable 28 rotatably driven in the rotary direction schematically depicted by the arrow shown thereon in FIG. 1. The strips 12, 14 may be first interconnected at their leading ends and then, while the turntable 28 and its carried mandrel 24are rotatably driven, helically wound upstanding on the mandrel outer surface 26 in alternate fashion to progressively axially build-up a grid structure 10 which throughout its length includes alternate coils of the strips 12, 14.

During this winding of the strips 12, 14, the juxtaposed wound coils thereof are progressively interconnected by successively connecting each segment 18 of the waved strip 14 with the there adjacent portion 12a of the adjacent wound coil of the planar strip 12, such connecting being performed at the locations (designed as 30 in FIG. 1) where the portions 12a of the strips l2, 14 are initially laid onto the mandrel surface 26 and while the portion 12a being connected is substantially locally heated. As shown in FIG. 1, these connections between the segments 18 and the portions 12a are preferably formed by welding through the employment of a conventional welding tool 30a which itself provides the substantial localized heating of the portions 12a during their connections. Alternatively, however, the connections between the portions 12a and segments 18 could be otherwise made (such as, for example, by riveting) in which event the portions 12a could be successively locally heated by a torch or other suitable means immediately prior to, or simultaneously with, their conneclions to the segments 18. The precise temperature to which the portions 124 are thus heated is not critical; however, such temperature should be sufficiently great that subsequent cooling of the portions 12a would cause significant shrinkage of the planar strip 12 were the latter not on the mandrel 24.

The substantially locally heated, connected portions 12a are each permitted to cool while their respective coil of the planar strip 12 is on the mandrel surface 26 such that the mandrel 24 prevents this cooling from re sulting in the permanent shrinkage of the planar strip 12 which would otherwise occur. Hence, as the wound coils of the planar strip 12 are incapable of shrinkage during cooling of the portions 12a, the inherent ductility of the planar strip 12 allowed these coils to stretch beyond the elastic yield stress of the material in compensation for the shrinkage; and this stretching of the coils of the planar strip 12 maintains the original length of the planar strip 12, as well as eliminates any residual non-uniform stress in the planar strip material which would otherwise cause distortion of the cylindrical shape of the grid structure after removal from the mandrel 24 In this manner, the strips 12, 14 continue to be wound and interconnected to progressively axially build-up the grid structure 10 to its full desired length while the heated, previously connected portions 12a of the planar strip 12 are permitted to cool on the mandrel outer surface 26. After the winding of the strips l2, 14 has produced an axially built-up grid structure 10 of the desired length, the trailing ends of the strips 12,14 may be interconnected; and the mandrel 24 and surrounding grid structure 10 are removed from the turn table 28. The removed grid structure 10 and mandrel 24 are schematically depicted in FIG. 2 of the drawings.

In the event that the employed mandrel 24 is of perforated annular construction, the thus formed structure is a drum of the type described in 'copending US. Pat. application and assigned to the assignee of this application Ser. No. 195,593 entitled DRUM COMPRISING SUPPORT MOUNTED GRID STRUCTURE which was filed by Rohe V. Pennington on the filing date of the present application.

In the event, however, that the mandrel 24 is of other construction, the grid structure 10 is normally separated from the mandrel 24. If the grid structure 10 be of stainless steel and the mandrel 24 of steel having a lower coefficient of thermal expansion, this separation may be readily accomplished by (as schematically depicted in FIG. 3) heating the grid structure 10 and mandrel 24 in a furnace 32 to a temperature at least about seven hundred degrees Farenheit and less than about twelve hundred degrees Farenheit for approximately five minutes or until differential thermal expansion sufficiently loosens the grid structure 10 from the mandrel 24 to permit its removal. The heated grid structure 10 is then (as schematically shown in FIG. 4) merely removed from around the mandrel 24 whereupon, after cooling, it may be employed as a filter drum, air drier drum or in any other suitable application. Although this method of separation of the grid structure 10 from the mandrel 24 is particularly beneficial in that it produces a desirable stress relief in the grid structure 10, the latter may alternatively be separated from the mandrel 24 in any other suitable manner. For example, the mandrel 24 may be disassembled into its component parts in the event that it be formed of segmental construction; or differential temperature processes can be employed to loosen the grid structure 10 from the mandrel 24, such processes comprising rapid heating of the grid structure 10 to a temperature higher than that of the mandrel 24 and/or cooling of the mandrel 24, for example, by fluid passed internal through cooling fluid passages.

The dimensional accuracy of the grid structure 10 produced by the method of the invention has been found to be significantly greater than possible with any prior method and, due to the accuracy of the provided grid structure 10, a substantial reduction is achieved in the amount of labor required for grinding or otherwise machining the inner and outer circumferences of the grid structure 10 to their final tolerances. In fact, in many instances the accuracy of the grid structure 10 provided by the method of the invention is sufficiently great to completely eliminate the necessity for machining of its circumferences. The economies inherent in this reduction or possible elimination of the machining facilitate the production of a more economical grid structure than previously possible. Also, as will be seen, the method of the invention permits the formation of distortion-free grid structures 10 at relatively high speed, thereby again facilitating the production of an economical grid structure 10.

It will be understood that, although only a single embodiment of the method of the invention has been schematically illustrated and hereinbefore described, the invention is not limited merely to this single embodiment but rather comtemplates other embodiments and variations within the scope of the following claims.

Having thus described my invention, I claim:

1. The method of making an annular grid structure from separate planar and connecting strip means, comprising the steps of progressively forming an axial buildup of the grid structure by winding the planar strip means in helical coils on a mandrel with the connecting strip means adjacent to the wound coils of the planar strip means,interconnecting the wound coils of the planar strip means and the connecting strip means while the wound coils of the planar strip means are substantially locally heated at the locations of the interconnections to a temperature sufficiently great that cooling of the planar strip means from such temperature would, in the absence of the mandrel, cause substantial shrinkage of the planar strip means, and permitting the substantially locally heated wound coils of the planar strip means to cool while on the mandrel to a temperature sufficiently low that the mandrel prevents permanent shrinkage of the planar strip means from occuring due to such cooling and the planar strip means resultantly stretches.

2. The method according to claim 1, further comprising the step of thereafter separating the axially built-up grid structure from the mandrel.

3. The method according to claim 2, wherein said separating of the grid structure from the mandrel is accomplished by heating the grid structure and the mandrel sufficiently to cause differential thermal expansion thereof to permit removal of the grid structure from the mandrel, and then removing the heated grid structure from the mandrel.

4. The method according to claim 2, wherein said separating of the grid structure from the mandrel is accomplished by disassembling the mandrel into component parts.

5. The method according to claim 2, wherein said separating of the grid structure from the mandrel comprises the step of creating a temperature in one thereof different from the temperature of the other thereof.

6. The method according to claim 1, wherein said localized heating of the planar strip means occurs as a result of said interconnecting.

7. The method according to claim 1, wherein said interconnecting is performed as the locations of the planar strip means to be connected are initially laid onto the mandrel.

8. The method according to claim 7, wherein said interconnecting is performed by welding.

9. The method of making an annular grid structure from separate planar and waved strips, comprising the steps of winding the strips helically on the annular outer surface of a mandrel whereby the wound strips progressively form an axial build-up of the grid structure around the mandrel outer surface, during said winding interconnecting adjacent coils of the strips by successively connecting portions of the planar strip with the waved strip while such portions are substantially locally heated to a temperature sufficiently great that cooling of the planar strip from such temperature would, in the absence of the mandrel, cause substantial shrinkage of the planar strip, and permitting the heated, connected portions of the planar strip to cool while wound on the mandrel to a temperature sufficiently low that the mandrel prevents pennanent shrinkage of the planar strip from occuring due to such cooling and the planar strip resultantly stretches.

10. The method according to claim 9, further comprising the step of thereafter separating the axially built-up grid structure from the mandrel.

11. The method according to claim 9, wherein the waved and planar strips are wound alternately arranged axially of the grid structure.

12. The method according to claim 9, wherein said connecting is performed as said portions of the planar strip to be connected are initially laid onto the mandrel.

13. The method according to claim 9, wherein said localized heating of said portions occurs as a result of said interconnecting.

14. The method according to claim 9, wherein said localized heating of said portions occurs as a result of said interconnecting, and said interconnecting is performed as said portions are each initially laid onto the mandrel. I

15. The method according to claim 14, wherein the said interconnecting is performed by welding.

16. The method according to claim 14, wherein the waved strip includes alternate diagonal segments with therebetween connecting segments on opposite sides of the central plane of the waved strip, and said interconnecting of the strips comprises welding said connecting segments of the waved strip to said portions of the planar strip whereby said portions are so substantially locally heated as a result of such welding.

17. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by heating the grid structure and mandrel to a temperature at least about seven hundred degrees Farenheit and less than about twelve hundred degrees Farenheit, and then removing the heated grid structure from the mandrel.

18. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by disassembling the mandrel into component parts.

19. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by creating a temperature in one thereof different from the temperature in the other thereof. 

1. The method of making an annular grid structure from separate planar and connecting strip means, comprising the steps of progressively forming an axial build-up of the grid structure by winding the planar strip means in helical coils on a mandrel with the connecting strip means adjacent to the wound coils of the planar strip means,interconnecting the wound coils of the planar strip means and the connecting strip means while the wound coils of the planar strip means are substantially locally heated at the locations of the interconnections to a temperature sufficiently great that cooling of the planar strip means from such temperature would, in the absence of the mandrel, cause substantial shrinkage of the planar strip means, and permitting the substantially locally heated wound coils of the planar strip means to cool while on the mandrel to a temperature sufficiently low that the mandrel prevents permanent shrinkage of the planar strip means from occuring due to such cooling and the planar strip means resultantly stretches.
 2. The method according to claim 1, further comprising the step of thereafter separating the axially built-up grid structure from the mandrel.
 3. The method according to claim 2, wherein said separating of the grid structure from the mandrel is accomplished by heating the grid structure and the mandrel sufficiently to cause differential thermal expansion thereof to permit removal of the grid structure from the mandrel, and then removing the heated grid structure from the mandrel.
 4. The method according to claim 2, wherein said separating of the grid structure from the mandrel is accomplished by disassembling the mandrel into component parts.
 5. The method according to claim 2, wherein said separating of the grid structure from the mandrel comprises the step of creating a temperature in one thereof different from the temperature of the other thereof.
 6. The method according to claim 1, wherein said localized heating of the planar strip means occurs as a result of said interconnecting.
 7. The method according to claim 1, wherein said interconnecting is performed as the locations of the planar strip means to be connected are initially laid onto the mandrel.
 8. The method according to claim 7, wherein said interconnecting is performed by welding.
 9. The method of making an annular grid structure from separate planar and waved strips, comprising the steps of winding the strips helically on the annular outer surface of a mandrel whereby the wound strips progressively form an axial build-up of the grid structure around the mandrel outer surface, during said winding interconnecting adjacent coils of the strips by successively connecting portions of the planar strip with the waved strip while such portions are substantially locally heated to a temperature sufficiently great that cooling of the planar strip from such temperature would, in the absence of the mandrel, cause substantial shrinkage of the planar strip, and permitting the heated, connected portions of the planar strip to cool while wound on the mandrel to a temperature sufficiently low that the mandrel prevents permanent shrinkage of the planar strip from occuring due to such cooling and the planar strip resultantly stretches.
 10. The method according to claim 9, further comprising the step of thereafter separating the axially built-up grid structure from the mandrel.
 11. The method according to claim 9, wherein the waved and planaR strips are wound alternately arranged axially of the grid structure.
 12. The method according to claim 9, wherein said connecting is performed as said portions of the planar strip to be connected are initially laid onto the mandrel.
 13. The method according to claim 9, wherein said localized heating of said portions occurs as a result of said interconnecting.
 14. The method according to claim 9, wherein said localized heating of said portions occurs as a result of said interconnecting, and said interconnecting is performed as said portions are each initially laid onto the mandrel.
 15. The method according to claim 14, wherein the said interconnecting is performed by welding.
 16. The method according to claim 14, wherein the waved strip includes alternate diagonal segments with therebetween connecting segments on opposite sides of the central plane of the waved strip, and said interconnecting of the strips comprises welding said connecting segments of the waved strip to said portions of the planar strip whereby said portions are so substantially locally heated as a result of such welding.
 17. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by heating the grid structure and mandrel to a temperature at least about seven hundred degrees Farenheit and less than about twelve hundred degrees Farenheit, and then removing the heated grid structure from the mandrel.
 18. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by disassembling the mandrel into component parts.
 19. The method according to claim 9, wherein the grid structure is thereafter separated from the mandrel by creating a temperature in one thereof different from the temperature in the other thereof. 